Study of the automated synthesis of the radiopharmaceutical 16 α [18F] fluoro-17β-estradiol

Abstract

Approximately 75% of breast cancer cells express estrogen receptor (ER +) and this type of cancer has incidence of 25 % a year, being the second cause of cancer death among women worldwide. The 16α-[18F]-fluoro-17β-estradiol, 18F-FES, is a lipophilic molecule with in vivo characteristics similar to estradiol being a valuable marker in molecular imaging for non-invasive diagnosis of primary and metastatic breast cancer using PET-CT, because it binds to estrogen receptors (ER binding). The objective of this work was to study the synthesis of 18F-FES in the GE TRACERlab® MXFDG module, using Chemical Kit and disposable cassette ABX® and determine the yield of the process and the analytical parameters to be employed in the routinely production of this radiopharmaceutical. The automated synthesis occurs in 75 min. and includes percolation of the [18F] fluoride in an anion exchange cartridge, elution of the cartridge, azeotropic drying in 3 steps, labeling using 3-methoxymethyl-16β,17β-epiestriol-O-cyclic sulfone (MMSE) and the hydrolysis in 1 step. Purification of the product is done in the module itself using solid phase extraction (SPE) cartridges, without the use of HPLC. The data about synthesis efficiency and quality control parameters are under analysis. Preliminary results suggest an increase in synthesis efficiency when minimal changes in the synthesis program were introduced. The results of quality control assays (radiochemical purity, residual solvent, radionuclidic purity and identity and chemical purity (TBA) suggest that final radiopharmaceutical meets the criteria established for other fluor-18 radiopharmaceuticals that have monographs in official compendia.